251 lines
8.6 KiB
Java
251 lines
8.6 KiB
Java
/*
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* Copyright 2021 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.buffer.api.pool;
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import io.netty.buffer.api.AllocatorControl.UntetheredMemory;
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import io.netty.util.internal.StringUtil;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.List;
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import static java.lang.Math.max;
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import static java.lang.Math.min;
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final class PoolChunkList implements PoolChunkListMetric {
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private static final Iterator<PoolChunkMetric> EMPTY_METRICS = Collections.emptyIterator();
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private final PoolArena arena;
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private final PoolChunkList nextList;
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private final int minUsage;
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private final int maxUsage;
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private final int maxCapacity;
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private PoolChunk head;
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private final int freeMinThreshold;
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private final int freeMaxThreshold;
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// This is only update once when create the linked like list of PoolChunkList in PoolArena constructor.
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private PoolChunkList prevList;
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PoolChunkList(PoolArena arena, PoolChunkList nextList, int minUsage, int maxUsage, int chunkSize) {
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assert minUsage <= maxUsage;
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this.arena = arena;
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this.nextList = nextList;
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this.minUsage = minUsage;
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this.maxUsage = maxUsage;
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maxCapacity = calculateMaxCapacity(minUsage, chunkSize);
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// the thresholds are aligned with PoolChunk.usage() logic:
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// 1) basic logic: usage() = 100 - freeBytes * 100L / chunkSize
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// so, for example: (usage() >= maxUsage) condition can be transformed in the following way:
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// 100 - freeBytes * 100L / chunkSize >= maxUsage
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// freeBytes <= chunkSize * (100 - maxUsage) / 100
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// let freeMinThreshold = chunkSize * (100 - maxUsage) / 100, then freeBytes <= freeMinThreshold
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//
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// 2) usage() returns an int value and has a floor rounding during a calculation,
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// to be aligned absolute thresholds should be shifted for "the rounding step":
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// freeBytes * 100 / chunkSize < 1
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// the condition can be converted to: freeBytes < 1 * chunkSize / 100
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// this is why we have + 0.99999999 shifts. A example why just +1 shift cannot be used:
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// freeBytes = 16777216 == freeMaxThreshold: 16777216, usage = 0 < minUsage: 1, chunkSize: 16777216
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// At the same time we want to have zero thresholds in case of (maxUsage == 100) and (minUsage == 100).
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//
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freeMinThreshold = maxUsage == 100 ? 0 : (int) (chunkSize * (100.0 - maxUsage + 0.99999999) / 100L);
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freeMaxThreshold = minUsage == 100 ? 0 : (int) (chunkSize * (100.0 - minUsage + 0.99999999) / 100L);
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}
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/**
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* Calculates the maximum capacity of a buffer that will ever be possible to allocate out of the {@link PoolChunk}s
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* that belong to the {@link PoolChunkList} with the given {@code minUsage} and {@code maxUsage} settings.
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*/
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private static int calculateMaxCapacity(int minUsage, int chunkSize) {
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minUsage = minUsage0(minUsage);
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if (minUsage == 100) {
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// If the minUsage is 100 we can not allocate anything out of this list.
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return 0;
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}
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// Calculate the maximum amount of bytes that can be allocated from a PoolChunk in this PoolChunkList.
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//
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// As an example:
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// - If a PoolChunkList has minUsage == 25 we are allowed to allocate at most 75% of the chunkSize because
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// this is the maximum amount available in any PoolChunk in this PoolChunkList.
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return (int) (chunkSize * (100L - minUsage) / 100L);
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}
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void prevList(PoolChunkList prevList) {
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assert this.prevList == null;
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this.prevList = prevList;
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}
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UntetheredMemory allocate(int size, int sizeIdx, PoolThreadCache threadCache, PooledAllocatorControl control) {
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int normCapacity = arena.sizeIdx2size(sizeIdx);
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if (normCapacity > maxCapacity) {
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// Either this PoolChunkList is empty, or the requested capacity is larger than the capacity which can
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// be handled by the PoolChunks that are contained in this PoolChunkList.
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return null;
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}
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for (PoolChunk cur = head; cur != null; cur = cur.next) {
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UntetheredMemory memory = cur.allocate(size, sizeIdx, threadCache, control);
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if (memory != null) {
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if (cur.freeBytes <= freeMinThreshold) {
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remove(cur);
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nextList.add(cur);
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}
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return memory;
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}
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}
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return null;
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}
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boolean free(PoolChunk chunk, long handle, int normCapacity) {
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chunk.free(handle, normCapacity);
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if (chunk.freeBytes > freeMaxThreshold) {
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remove(chunk);
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// Move the PoolChunk down the PoolChunkList linked-list.
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return move0(chunk);
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}
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return true;
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}
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private boolean move(PoolChunk chunk) {
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if (chunk.freeBytes > freeMaxThreshold) {
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// Move the PoolChunk down the PoolChunkList linked-list.
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return move0(chunk);
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}
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// PoolChunk fits into this PoolChunkList, adding it here.
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add0(chunk);
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return true;
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}
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/**
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* Moves the {@link PoolChunk} down the {@link PoolChunkList} linked-list, so it will end up in the right
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* {@link PoolChunkList} that has the correct minUsage / maxUsage in respect to {@link PoolChunk#usage()}.
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*/
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private boolean move0(PoolChunk chunk) {
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if (prevList == null) {
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// There is no previous PoolChunkList so return false which result in having the PoolChunk destroyed and
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// all memory associated with the PoolChunk will be released.
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return false;
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}
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return prevList.move(chunk);
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}
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void add(PoolChunk chunk) {
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if (chunk.freeBytes <= freeMinThreshold) {
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nextList.add(chunk);
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return;
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}
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add0(chunk);
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}
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/**
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* Adds the {@link PoolChunk} to this {@link PoolChunkList}.
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*/
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void add0(PoolChunk chunk) {
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chunk.parent = this;
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if (head == null) {
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head = chunk;
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chunk.prev = null;
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chunk.next = null;
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} else {
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chunk.prev = null;
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chunk.next = head;
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head.prev = chunk;
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head = chunk;
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}
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}
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private void remove(PoolChunk cur) {
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if (cur == head) {
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head = cur.next;
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if (head != null) {
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head.prev = null;
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}
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} else {
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PoolChunk next = cur.next;
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cur.prev.next = next;
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if (next != null) {
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next.prev = cur.prev;
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}
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}
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}
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@Override
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public int minUsage() {
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return minUsage0(minUsage);
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}
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@Override
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public int maxUsage() {
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return min(maxUsage, 100);
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}
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private static int minUsage0(int value) {
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return max(1, value);
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}
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@Override
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public Iterator<PoolChunkMetric> iterator() {
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synchronized (arena) {
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if (head == null) {
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return EMPTY_METRICS;
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}
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List<PoolChunkMetric> metrics = new ArrayList<>();
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for (PoolChunk cur = head;;) {
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metrics.add(cur);
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cur = cur.next;
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if (cur == null) {
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break;
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}
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}
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return metrics.iterator();
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}
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}
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@Override
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public String toString() {
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StringBuilder buf = new StringBuilder();
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synchronized (arena) {
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if (head == null) {
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return "none";
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}
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for (PoolChunk cur = head;;) {
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buf.append(cur);
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cur = cur.next;
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if (cur == null) {
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break;
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}
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buf.append(StringUtil.NEWLINE);
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}
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}
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return buf.toString();
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}
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void destroy() {
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PoolChunk chunk = head;
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while (chunk != null) {
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chunk.destroy();
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chunk = chunk.next;
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}
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head = null;
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}
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}
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